1. Field of the Invention
The present invention relates to a drying scale. More particularly, the present invention relates to a drying scale that contains a scale pan that is supported on a weighing system and that has a radiating source for heating and drying weighing material placed on the scale pan. In addition, the present invention relates to a method performed by the drying scale. The following disclosure is based on German Patent Application No. 19854563.0 which was filed on Nov. 26, 1998 and which is incorporated herein by reference.
2. Description of the Related Art
Examples of scales that contain a radiating source for drying samples to be weighed are generally described in U.S. Pat. No. 4,666,007 ("the '007 patent") and U.S. Pat. No. 4,889,201 ("the '201 patent"). Both the '007 patent and the '201 patent are incorporated herein by reference.
As described in the '007 patent, the drying scale is designed such that the radiating source does not obstruct the scale pan when a sample to be weighed is loaded on the scale pan. Specifically, the radiating source is arranged behind the scale pan, and after the sample is loaded onto the pan, a deflecting reflector is unfolded. Then, the thermal radiation produced by the radiation source is reflected via the deflecting reflector onto the scale pan to dry the sample. Afterwards, when the sample is dried, the deflecting reflector is folded away from the sample pan. Although the radiating source is located behind the scale pan so that it does not obstruct the scale pan, a large space exists between the radiating source and the scale pan. Thus, the thermal radiation generated by the source is weakened due to the distance that it must travel to the scale pan and due to reflection losses when it is deflected by the deflecting reflector. Accordingly, the energy efficiency of the drying scale described in the '007 patent is not optimum.
An example of a drying scale that attempts to overcome the above problem is shown in U.S. Pat. No. 5,787,600 ("the '600 patent") which is incorporated herein by reference. As described in the patent, the drying scale contains a scale pan that is located directly below the radiating source when the sample in the pan is being dried. Also, when the sample is to be loaded onto the scale pan, the scale pan is moved out from underneath the radiating source. However, when the scale pan is moved with respect to the radiation source for the purposes of the loading the sample, the weighing system does not move. Thus, a complicated connection, which can be extended and retracted telescopically, between the scale pan and weighing system is required. However, such a complicated connection is extremely susceptible to vertical vibrations and degrades the accuracy of the drying scale.
To attempt to overcome such problem, the '600 patent describes another embodiment in which both the weighing system and scale pan move from underneath the radiating source when a sample is to be loaded into the scale pan. However, such a design does not adequately overcome the above problem because, when the weighing system is moved out from underneath the radiating source, it is very sensitive to vibrations because it extends out from the drying scale. In addition, the various components used to guide the weighing system between the drying position and the loading positing must be extremely precise since the horizontal position of the weighing system must be exactly the same when it is in the drying and loading positions. Therefore, the complexity and cost of the drying scale is substantially increased.